96 BACTERIOLOGY FOR NURSES 



Predisposing Causes of Tuberculosis. It is said 

 that in no other known disease do predisposing fac- 

 tors figure so largely as in tuberculosis. 



Indoor occupations under unsanitary conditions, 

 such as bad air, insufficient light, dampness, and long 

 hours of work, are especially conducive to all forms 

 of tuberculosis. It was formerly thought that by 

 heredity many persons were tuberculous, but this is 

 now disputed, and it is believed that the intimate 

 relations of parents and children living under the 

 same conditions accounts for the infection. Alcohol- 

 ism, with all that goes with it, is a predisposing factor, 

 also the wasting diseases, as diabetes and typhoid 

 fever, are often followed by phthisis, but the most 

 important factor of all is uncleanliness combined 

 with poor food and bad air in the homes. 



Tuberculin. In 1890 Robert Koch announced 

 his preparation known as Tuberculin R. as a 

 curative agent. Tuberculin is the filtered products 

 of growth from cultures of tubercle bacilli. When 

 injected under the skin of a healthy person, no re- 

 action occurs, but when used upon a tuberculous per- 

 son or animal, a pronounced reaction occurs, consisting 

 of a sudden elevation of temperature and a marked 

 hypersemia about the tuberculous focus, followed 

 by disintegration of the tuberculous mass. 



